Wallboard formed of a rigid core sandwiched between facing layers is well known in building construction. It is used as a surface, both exterior and interior, for walls and ceilings, roofs and siding, as tile backer and in many other applications. Historically, cellulosic (paper-based) facers have been common but more recently fiberglass facers have been used for their superior dimensional stability, resistance to water, weatherability, resistance to mold and other advantages.
Polyisocyanurate boards, gypsum boards, and polystyrene boards are widely used in the construction of interior walls in homes and office buildings. Such construction boards have come into widespread use because they are a low cost alternative to other products and offer a unique combination of benefits. For instance, construction boards are easy to handle and can be cut to cover the shape of virtually any interior wall surface while requiring minimal labor. Additionally, wall boards of this type are light weight, making it easy for professional construction workers and homeowners to use them. Gypsum wall board also offers a high level of fire resistance and sound barrier characteristics. Construction boards can also be painted and will readily accept wallpaper. Additionally, gypsum wall board exhibits a very low level of expansion and contraction with changing temperature and/or humidity levels. Accordingly, gypsum wall board is highly resistant to cracking.
Gypsum is actually hydrous calcium sulfate (CaSO4.2H2O) which is also known as karstenite, muriacite, anhydrous sulfate of lime, and anhydrous gypsum. In making gypsum board, wet gypsum is generally formed into a sheet between two paper layers known as facers. The paper facers accordingly form the outer surfaces of the gypsum board sheets. These sheets normally have a thickness of about 0.5 inch or ⅝ inch and are four feet in width and eight feet or twelve feet in length. High impact strength gypsum wall board is made by imbedding a layer of fiberglass mesh in the gypsum. Wall boards can also be manufactured utilizing polystyrene or polyisocyanurate in lieu of gypsum in making the rigid sheet of the wallboard. The facers of this invention can also be used in making polyisocyanurate boards, polyurethane boards, and polystyrene boards for roofing insulation. These materials offer the advantages of high water resistance, ultraviolet light resistance and fungal resistance.
Paper facers have low water resistance and weatherability and are also not dimensionally stable. Also, paper facers can be destroyed by bacterial and/or fungal growth. Thus, paper facers are not totally satisfactory in applications where they may be exposed to water or high levels of humidity.
Gypsum wallboards, polyisocyanurate wallboards (isoboards), and polystyrene wallboards all offer an array of advantages in various applications. However, their utility and service life can be compromised by the traditional problems associated with paper facers. For instance, paper facers do not provide a satisfactory barrier to liquid water and are susceptible to bacterial and fungal growth.